(Updates with quotes from family attorney)
By Elizabeth Daley
MURRYSVILLE, Pa., April 10 (Reuters) - Pennsylvania officials sought a motive on Thursday for what may have driven a 16-year-old student to turn on his classmates with two kitchen knives, stabbing startled victims in the stomach and back and leaving nearly two dozen wounded.
Sophomore Alex Hribal was charged with attempted homicide and aggravated assault after allegedly using 8-inch steel blades in a stabbing frenzy through the hallways of Franklin Regional High School in Murrysville near Pittsburgh on Wednesday.
A security guard and 21 students were wounded before the suspect was tackled by an assistant principal, officials and students said.
Three teenage boys remained hospitalized in critical condition with stab wounds, while other survivors and witnesses struggled on Thursday to find an explanation for the attack.
The teen had no psychiatric or disciplinary problems, and his family described him as a good student who played hockey and mingled well with others, said family lawyer Patrick Thomassey.
"He's upset. He can't believe he did this," Thomassey told reporters outside Westmoreland County Juvenile Detention Center where he had a meeting with the teen.
"He's scared and remorseful," he said. "He hurt his friends."
Hribal spent the night before the attack with his parents, who the attorney described as "devastated."
"They certainly didn't see this coming," he said. "He's just a good kid and he comes from a great family."
The lawyer said he wants the teen to undergo psychiatric evaluation and to be moved into the juvenile court system. He has been charged as an adult.
"We have to figure out why this happened," Thomassey said.
Student athlete Brett Hurt, 16, described how he was goofing around with a friend before classes in the crowded hallway when suddenly it was filled with screams and, moments later, he was stabbed in the back.
"That's just when everything went into straight chaos," he told reporters at the hospital where he was being treated for his wound and a bruised lung. "What was going through my mind? Will I survive - or will I die."
He said a friend helped him into a classroom and applied pressure to the wound to stanch the bleeding. Hurt, a weight lifter, said he had met Hribal only a couple of times, but harbored no ill will toward him.
"I've been thinking, maybe if he had more friends or somebody to help him out, to show him a different path. Maybe it would have been different," he said.
While the United States in recent years has seen numerous large-scale shootings in public places, including schools, movie theaters and shopping areas, mass stabbings are less common.
Police and the FBI on Wednesday searched the suspect's home. Neighbors said both parents work, and the teen has a brother who also attends Franklin Regional High School.
The high school will be closed, probably until Monday, while police conduct an investigation, officials said.
Murrysville Police Chief Tom Seefeld told CNN that authorities were investigating a report of a threat made the night before the stabbings, but had no evidence to support that.
Most of the victims were 14 to 17 years old.
Among the most seriously injured was a 17-year-old boy, who remained in critical condition following surgery at UPMC Presbyterian, a hospital spokeswoman said. A knife blade passed through his liver, diaphragm and some major blood vessels but missed his heart and aorta.
Eight other teenage boys were recovering in two other hospitals, including two who were in critical condition and may require more surgery.
Hribal faces four counts of attempted homicide and 21 counts of aggravated assault, police said. He was ordered to face a preliminary hearing in seven to 10 days. (Reporting by Elizabeth Daley in Murrysville, Pennsylvania, Jonathan Allen in New York, Dave Warner in Philadelphia, Brendan O'Brien in Milwaukee, and Doina Chiacu in Washington; Writing by Eric M. Johnson; Editing by Scott Malone, John Stonestreet, Bernadette Baum, Ellen Wulfhorst and Gunna Dickson)